The objective of this project is to develop an in vitro model system for the study of aging-related biochemical changes and to correlate these changes with in vivo changes in humans. Fibroblasts from subjects with juvenile diabetes are the model of choice because the genetic defect in diabetes is believed to be expressed in the accelerated senescence of fibroblasts in vitro. Collagen synthesis was selected as the biochemical marker of aging because it is involved in the pathogenesis of both diabetic angiopathy and arteriosclerosis which are aging related diseases. Studies of aging in vitro (cell and population doublings, plating efficiency and DNA synthesis) and collagen synthesis (14C proline incorporation and hydroxylation followed by amino acid analysis and "procollagens" monitored by SDS Gel electrophoresis) are in progress. Small but significant differences in in vitro aging between normal and diabetic cells have been found. Preliminary studies indicate that proline hydroxylation is greater in diabetic than normal cells. This is confirmed by the increased amounts of procollagen formation and 14C proline incorporation found by electrophoresis.